The arm curls on a machine are specifically designed to target the biceps, offering a focused and controlled workout to build strength and definition in the upper arms. Using adjustable weights, the machine provides consistent resistance throughout the movement, ensuring optimal muscle engagement. The ability to modify the weight load allows users to tailor the intensity to their fitness level, making it suitable for both beginners and advanced lifters. This feature also facilitates gradual progression, enabling effective muscle growth and enhanced arm strength over time.